enforcer-rules/src/site/apt/requireSameVersionsReactor.apt.vm

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  ------
  Require Same Versions Reactor
  ------
  Karl-Heinz Marbaise
  ------
  March 2014
  ------

Require Same Versions Reactor

  This rule checks that the versions within the reactor are consistent furthermore
  it will check that every module within the project contains a parent and that the 
  parent is part of the reactor build. Furthermore it will all given dependencies
  if they are intermodule dependencies that they using the same versions. 


  The following parameters are supported by this rule:
   
  * message - an optional message to the user if the rule fails.
    
   []

   
  Sample Plugin Configuration:
  
+---+
<project>
  [...]
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-enforcer-plugin</artifactId>
        <version>${project.version}</version>
        <executions>
          <execution>
            <id>enforce-no-snapshots</id>
            <goals>
              <goal>enforce</goal>
            </goals>
            <configuration>
              <rules>
                <requireSameVersionsReactor/>
              </rules>
              <fail>true</fail>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
  [...]
</project>
+---+

  There are different situations within a multi module build which can lead to problems
  (for example not working with maven-release-plugin etc.).
  This rule is intended to prevent such problems.
  
  Let us assume we have the following (simple) project structure for a multi module setup.

+-----
   root (pom.xml)
     +--- module1 (pom.xml)
     +--- module2 (pom.xml)
+-----

  The root <<pom.xml>> looks like this:
  
+-----
  <groupId>com.mycompany.project</groupId>
  <artifactId>parent</artifactId>
  <version>1.0-SNAPSHOT</version>
  (..)
+-----

  The best practice in Maven is that all childs inherit the version from their parent 
  and don't define a new version which looks like this:
  
+-----
  <parent>
    <groupId>...</groupId>
    <artifactId>...</artifactId>
    <version>1.0-SNAPSHOT</version>
  </parent>

  <artifactId>module1</artifactId>
  (..)
+-----  

  But sometimes people mistaken things or violate the best-practice and  
  this look like this:

+-----
  <parent>
    <groupId>...</groupId>
    <artifactId>...</artifactId>
    <version>1.0-SNAPSHOT</version>
  </parent>
  
  <artifactId>module1</artifactId>
  <version>1.1-SNAPSHOT</version>
+-----

  By using this rule you would get a message during the build if you try to build
  and example like the above which result in the following output:

+-----
[WARNING] Rule 0: org.apache.maven.plugins.enforcer.RequireSameVersionsReactor failed with message:
The reactor contains different versions.
 --> org.apache.enforcer.example:appasm:pom:1.1.0-SNAPSHOT
+-----